Magnetic resonance spectroscopy findings in non-enhancing desmoplastic medulloblastoma

Abstract

Medulloblasoma is a common posterior fossa tumor seen in children and presents with some typical features like midline vermian location and fairly homogeneous enhancment. Desmoplastic variety of medulloblastoma is usually seen in the adults and is known to show some atypical features like lateral cerebellar location, variable enhancement, and early meningeal infilteration. Therefore medulloblastoma should always be considered in differential diagnosis of posterior fossa mass in adults even when typical imaging findings are not that of medulloblastoma. Enhancement pattern can be variable in these tumors varying from mild to striking. Occasionally, totally non-enhancing tumors are encountered, which can cause further diagnostic confusion. We describe the magnetic resonance (MR) and MR spectroscopy findings in a case of midline vermian mass, which did not show any enhancement on post-contrast images, and was subsequently proven to be desmoplastic medulloblastoma. On MR spectroscopy, the mass showed elevated choline peak consistent with mitotic lesion. No significant lipid lactate leak was seen, which is also consistent with the ususally homogeneous nature of these tumors. Moreover, it displayed taurine peak at 3.4 ppm which is considered fairly specific for medulloblastoma. Therefore, MR spectroscopy findings can be helpful in the diagnosis of medulloblastoma in adults when MR imaging findings can be nonspecific.

Keywords: Desmoplastic; MR spectroscopy; medulloblastoma.

Figure 1

Axial T2W (a) and FLAIR (b) images show homogeneously hyperintense midline vermian mass. Sagittal T2W (c) images show mild upward displacement of superior medullary velum by the mass

Figure 2

Axial pre contrast (a) and axial (b) post-contrast images show no enhancement in the mass

Figure 3

Proton MR spectroscopy image showing prominent choline peak. Taurine peak is seen at 3.4 ppm